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Brown, Sarah Elizabeth orcid.org/0000-0002-9715-3980 (2019) The Medieval Glazier at Work. In: Carson Pastan, Elizabeth and Kurmann-Schwarz, Brigitte, (eds.) Investigations in Medieval Stained Glass. Reading Medieval Sources . Brill , Leiden and Boston , pp. 9-22.

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in England with Hints on Glass Painting, makes it clear

that Winston’s intention was not only to provide a clas-

sified typology of medieval stained-glass design, but also

to influence contemporary glazing practices. Hendrie’s

critical notes are those of an historian and literary schol-

ar. Winston’s are those of a man who had examined me-

dieval glass at close quarters, who knew the workings of

a glass- house and the practices of a glazing workshop.

Winston considered his text to be an important

source book for those engaged, like himself, in the pro-

motion of a revival of manufacture of “antique” glasses

and authentic medieval painting styles. For this reason,

he provided parallel extracts from other authors, an-

cient and modern, including Heraclius (10th century)

and Bontemps (19th century). Frustrated by what he

recognised as inconsistencies and omissions in Theoph-

ilus’s text, Winston was the first writer to test his read-

ing of Theophilus against both his own experience of

medieval windows and a reading of medieval glazing

accounts and contracts.4 The dichotomy between an

emphasis on literary and linguistic scholarship and the

implications of the text for an understanding of practi-

cal application, can still be seen in the contrasting ap-

proaches of the two modern editions of Theophilus in

English translation: C.R. Dodwell’s scrupulous 1961 edi-

tion of parallel Latin and English texts; and Hawthorne

and Smith’s 1963 English translation with its many mod-

ern technical drawings.5

Despite the critical examination of other significant

textual sources (notably that of Italian glazier Antonio

da Pisa), the 12th- century treatise has continued to dom-

inate the discourse, even though Theophilus was writing

before the development of complex stone tracery (in the

13th century), before the age of silver stain (introduced in

the early 14th century), before the widespread adoption

of abrasion and etching techniques (predominantly in the

15th and 16th centuries), and before the use of paper in

the preparation of designs (from the second quarter of the

15th century); all processes relevant to window produc-

tion in the later Middle Ages. From the middle of the 20th

century a new generation of scholars began to redress

this balance by enquiring into glazing practice beyond

The (re)discovery in the mid- 19th century of the com-

plete 12th- century text now widely known as De Diversis Artibus, by the pseudonymous author, priest and monk

“Theophilus”, triggered scholarly interest in the manu-

facturing techniques of the medieval glazier in exactly

the period in which the Gothic Revival in stained glass

was reaching its height.1 All subsequent art- historical

perceptions of the technical aspects of the medium have

been dominated by the most coherent medieval de-

scription of glass making and glazing practice in the me-

dieval period, contained in Book 2 of Theophilus’s text.

Until very recently, the numerous modern descriptions

of how a medieval window was made were augmented

by assumptions derived from craft practice of the later

19th century. Recent scholarship, much of it under the

aegis of the international Corpus Vitrearum, founded

in 1952, has encouraged revisionary studies of medieval

glazing technologies. Scholars have now revisited the

seminal texts on which our understanding of medieval

glazing technique has been founded, while conservators

have observed and documented the physical evidence

of glaziers and glass- painters at work.2 This paper will

revisit the evidence for medieval glazing practice from

these new perspectives.

1 Theophilus and the Historiography

of the Medieval Craft

For the English- language readership, Theophilus’s trea-

tise first became accessible through Robert Hendrie’s

1847 parallel Latin and English texts of all three books.

However, the most important edition was that pub-

lished as part of Charles Winston’s seminal history of

the stylistic development of medieval stained glass in

England, a two- volume work with meticulous, archaeo-

logically correct illustrations, in which Book Two of The-

ophilus’s text was translated, with extensive notes.3 The

full title of Winston’s book, An Inquiry into the Difference of Style Observable in Ancient Glass Painting, especially

chapter 1

The Medieval Glazier at Work

Sarah Brown

1 See Raguin, “The reception of Theophilus”, pp. 11– 28.

2 See Kurmann- Schwarz, Ch. 20 in this volume.

3 Winston, An Inquiry, pp. 311– 41. Although aware of earlier German

scholarship, Winston worked from l’Escalopier’s 1843 French

edition.

4 Winston, An Inquiry, pp. 342– 50.

5 All citations here will refer to the Dodwell translation, The Various

Arts.



10 Brown

between art historians and materials scientists is provid-ing the social and historical context for observation on the chemical composition of medieval bulk glasses, with exciting implications for our understanding of networks of stained- glass manufacture and distribution.13

2 Building the Walls of the Heavenly Jerusalem

While Theophilus opens his discussion of window- making processes with a description of the medieval glass- house, it is clear that glassmaking and window- making were quite distinct and separate processes.14 The glazier was thus always once removed from the manu-facture of his most important raw material, and in some ways in thrall to his supplier for the qualities and colours of his palette of materials. Antonio da Pisa’s discussion of the making of pot- metal coloured glasses is thus, per-haps understandably, flawed, as he is describing the ex-pertise of others. Modern research into the composition and manufacture of medieval window glass has shown that a remarkable array of glass colours were made from a very limited range of compositional elements. The only metallic oxide described as having been added de-liberately in order to colour glass, is copper. The other key colouring agents were manganese and iron, both of which were present coincidentally, as part of the com-position of the sand and the wood ash (especially in the ash of beech wood advocated by Theophilus) of which typical medieval potash- lime- silica glasses were made. While the medieval glass- maker had no control over the presence of these compositional elements, it has been suggested that he may have had some empirical control over the degree of oxidation of the materials during the melting process.15 Recent research has demonstrated that this may have been particularly critical in the man-ufacture of translucent ruby glasses, challenging the as-sumption that they were always manufactured through the lamination process commonly known as “flashing”.16

It is clear that glaziers and their patrons were sensi-tive to the properties and qualities of glass from different sources, and may have sought them out for these very reasons; Antonio singles out the flashed ruby glasses of Germany as being particularly good for the application of acid etching.17 The fabric accounts of English projects are especially helpful in this regard, as no coloured glasses

Theophilus. Glimpses can be gleaned from examining the full gamut of texts and treatises, but also from wills, con-tracts and medieval glazing accounts, and from the win-dows themselves, all of which provide a pragmatic and material counterpoint to the literary sources, although not without their own challenges of interpretation.

Thanks to the indefatigable archival research of L.F. Salzman, a scholarly overview of the documentary evi-dence for medieval glazing practice in England became accessible.6 In the last decade of the 20th century the fruits of documentary and archival research began to make their mark on a rising tide of studies of medieval glazing practice, while the Corpus Vitrearum promoted international collaborations involving art historians, glaziers, scientists and conservators.7 Strobl’s doctoral research, published in 1990, carried particular authori-ty because of the author’s dual training in history of art and craft and conservation practice.8 In 1991, Brown and O’Connor contributed a book on medieval glass paint-ers to a British Museum series of nine titles on medieval craftsmen, and in the same year Marks contributed on window glass in one of 15 chapters of a study of English medieval industries.9 The Antonio da Pisa project, pub-lished in 2008, not only provided a new scholarly edition and commentary of Antonio’s rather overlooked techni-cal treatise (juxtaposed with invaluable translations of all other relevant texts), but brought together a team of craftsmen, conservators and scholars who not only subjected the texts to rigorous scrutiny, but also tested and reflected upon the processes described by Antonio, known to have been a practising glazier.10 In Belgium technical research has focused, among other things, on the production techniques involved in the manufacture of roundels and unipartite panels.11 Corpus Vitrearum researchers in Germany and the usa have reassessed the historical evidence for the use of acids to etch the surfaces of coloured flashed glasses.12 Conservators and scholars working in the usa, Britain, and Switzerland have observed evidence of sophisticated methods for the transfer of designs from the cartoon to the glass, dis-cussed more fully below. Interdisciplinary collaboration

6 Salzman, Building in England Down to 1540, published in 1952.

Also see id., “The glazing of St Stephen’s Chapel”; and id., “Me-

dieval glazing accounts”. Now see Brooks and Evans, The Great

East Window, pp. 11– 16 and 33– 36.

7 Signaled in Boulanger and Hérold (eds.), Le vitrail et les traités;

Pilosi, Shepard, and Strobl (eds.), The Art of Collaboration.

8 Strobl, Glastechnik des Mittelalters.

9 Brown and O’Connor, Glass- Painters; Marks, “Window glass”.

10 Lautier and Sandron, Antoine de Pise.

11 Caen, Production of Stained Glass.

12 Scholz et al., “Beobachtungen zur Ätztechnik”; Pilosi et al.,

“Early acid- etching”.

13 Freestone et al., “Multi- disciplinary investigation”.

14 Theophilus, The Various Arts, pp. 37– 43.

15 Royce- Roll, “The colors of Romanesque stained glass”.

16 Kunicki- Goldfinger et al., “Technology, production and

chronology”.

17 Lautier and Sandron, Antoine de Pise, p. 73.



The Medieval Glazier at Work 11

In France in the same period, there is plentiful doc-umentary evidence for the existence of small scale “patterns” (variously called poutraict, patron au petit pied and gect) provided by the patron for the use of the glaziers. These sketches carried legal weight and were appended to the contract, which was thereby free to define costs, specification of materials, timescales, and penalties.24 A small number of sketch designs for late- medieval windows have survived, shedding light on the process of negotiation between the patron and the glazier. Sometimes called a “vidimus” (“we have seen”), these preliminary drawings are remarkable for the variety and diversity of information they convey.25 One late 15th- century example preserved in the British Library (Figure 1.1), was probably drawn by the donor himself and concerns the appearance of the donor im-ages of Sir Thomas Froxmere and his wife, which were to be positioned at the base of an unidentified window then under discussion.26 However, most sketches are actually the work of extremely competent professional artists. Some have a grid superimposed to assist in scal-ing up the design to full size, and some are marked with the position of structural window bars. Few are fully coloured and none indicate the internal leading pat-tern essential in the actual construction of a stained- glass panel.

The small- scale sketch had serious shortcomings in conveying complex heraldic information for monu-mental glazing schemes. While patrons could probably expect experienced glaziers to be familiar with all but the most unusual or novel iconographic formulae, they seem to have been less confident in leaving details of he-raldic display to chance. Thomas Froxmere’s vidimus is almost exclusively concerned with heraldic detail, per-haps understandably, as the heraldry of a minor coun-try gentlemen is unlikely to have been well- known. In 1505 Lady Margaret Beaufort, mother of King Henry vii, paid the London artist William Hollmer 20 pence for a drawing of a heraldic yale, to be sent to the Peterbor-ough glazier John Delyon, who had depicted the beast incorrectly as “a common antelope” in the glazing of the great hall of her manor house at Collyweston. Delyon received 7s to correct his mistake.27 This may explain why a number of designs for monumental stained-glass projects – for example Hans von Kulmbach’s design for a window (c.1522) for Jacob Welser and Ehrentraud Thu-mer in the Mariakirche in Nuremburg – leave the coats

were manufactured in England until the late 15th centu-ry, meaning that the glaziers needed to be specific about their sources of supply. References to coloured glass from Burgundy, Hesse, Lorraine, Normandy, and even Venice are found in English accounts.18 The executors of Richard Beauchamp specified a wide range of coloured glasses that were to be used for glazing the Beauchamp Chap-el: blue, yellow, red, purple, sanguine, violet, green, and white, of the finest quality and foreign manufacture. The use of English glass was expressly forbidden!19

3 Patrons and Patterns

Frustratingly, the first, and in some respects the most in-triguing, stage in the creation of a window, the negotia-tion between the patrons and their craftsmen, is omitted from Theophilus’ instructions. We are not told how gla-ziers were instructed to fill their windows, nor are the few surviving medieval contracts especially helpful in this re-gard, referring only obliquely to a design process that had already been determined. John Thornton, commissioned to make the Great East Window of York Minster between 1405 and 1408, was instructed merely to fill the window “with historical images and other painted work”, a rather impoverished description of one of Europe’s largest and most ambitious windows.20 The accounts for the glazing of the collegiate church of the Holy Trinity at Tatteshall in Lincolnshire do describe the subjects of the windows, albeit briefly: the Legend of the Holy Cross, St. James, the Creed, the Magnificat, and the Seven Sacraments. But this seems to have been intended to distinguish the windows assigned to each of the five teams of glaziers entrusted with the work, rather than to invoke the appearance of the windows themselves.21 Reference to other prestigious and well- known projects underpinned the discourse. At Westminster glaziers had other useful drawings to inform their understanding of their patron’s requirement, for in 1509 “pictures” of “Stores, Ymagies, Armes, Bagies and Cognissaunts” had been delivered to the master of the royal works at Westminster, in accordance with Henry vii’s will.22 Executors charged with the commissioning of memorial windows were sometimes provided with tes-tamentary instructions and even drawings that reflected the wishes of the deceased.23

18 Brown and O’Connor, Glass- Painters, pp. 47– 48.

19 Myers, “The contracts for the making of the tomb of Richard

Beauchamp”.

20 French, The Great East Window, pp. 153– 54.

21 Marks, Holy Trinity, Tattershall, pp. 30– 58.

22 Marks, “Henry VII’s chapel”, p. 190.

23 Marks, “Wills and windows”, pp. 248, 250.

24 Leproux, Recherches sur les peintres- verriers parisiens, p. 35.

25 Wayment, “The great windows”.

26 London, British Library, Ms Lansdowne 874, fol. 191; Goodall,

“Two medieval drawings”, pp. 160– 62.

27 Salzman, Building in England, p. 178.



12 Brown

Fairford, c.1500, for example, the block- book Biblia Pau-perum, devised in the Netherlands c.1464– 65, was used as a source for stained-glass design, presumably at the behest of the patron.31 A remarkable interpretation of 1502 of the Tuscan poet Petrarch’s Triumphs in stained glass, for the church of Saint- Pierre at Evry- le- Châtel (Aube), has been shown to be indebted to both early printed books of hours and to even more cheaply print-ed tarot cards, used in a popular game originally known as Ludus Triumphorum.32

Perhaps the most remarkable evidence of the power of print to transform stained-glass design is the speed and degree to which designs by Nuremberg artist Albrecht Dürer circulated throughout Europe. The Apocalypse window in the church of Saint- Georges at Chavanges (Aube) of 1526 is clearly indebted to Dürer’s Large Passion of 1498, one of several windows copying this same source in the Champagne region.33 Three scenes in the east win-dow of Balliol College, Oxford, including the Ecce Homo (Figure 1.2), dated only three years later, are also based on Dürer’s engraved Passion (1507– 13), while the Carrying of the Cross is indebted to the Great Passion. The win-dow was given by Laurence Stubbs, almoner and build-ings administrator in the household of Cardinal Thom-as Wolsey, whose brother Richard was master of Balliol College.34 Wolsey is known to have owned an engraved copy of Dürer’s Passion. Perhaps not surprisingly, some of the closest interpretations in glass of sources circulating in engravings were in the form of small- scale roundels, often destined for secular and domestic settings. A single sheet of clear glass could very easily be placed over an en-graving in order to paint a direct copy. Glaziers collected these engravings to copy, adapt and share with their cli-ents, and probably made several sets of the most popular series in anticipation of easy sales, as, unlike monumen-tal stained- glass panels, roundels could easily be accom-modated into plain glazed surrounds.35

Armed with these preliminary drawings, or engraved sources, the patron could enter into negotiations for the actual making of the window with his or her chosen glazing workshop. A shared experience of other glazing schemes provided a bedrock on which these discus-sions were undoubtedly founded. This is implied in the

of arms of the kneeling donors blank.28 The drawing is a highly finished clean copy that was very little altered in translation into stained glass, but additional heraldic drawings would have been required in order to complete the commission. In summary, we are forced to conclude that sketch designs served different purposes, represent different stages in a process, and above all reflect the wishes of different kinds of patrons whose personal pri-orities and budgets varied a great deal.

Only rarely do we glimpse the research that had pre-ceded the commissioning of the preliminary design. A late 12th- century illuminated Life of St. Cuthbert from the monastic library of Durham Cathedral priory was loaned to Archbishop Richard Scrope of York (1398– 1405), presumably to inform the devising of the version of the saint’s life destined to fill the south- east transept of York Minster (SV7).29 In the early 16th century the newly- built chapel of the Observant Friars at Greenwich (consecrated c.1494) also served as the chapel for Henry vii’s Greenwich Palace. Two rolls preserved in the Brit-ish Library record the results of preparatory research undertaken in anticipation of the instruction of glaziers soon to be entrusted with the creation of a new five- light east window.30 The window was to include half- length figures of Henry vii and Queen Elizabeth, the princess Margaret and the king’s mother, Lady Margaret Beaufort. The saints to be depicted flattered the newly established Tudor dynasty by reflecting the devotional interests and political preoccupations of the royal family, but were also appropriate for a Franciscan community. The coats of arms of the saints to be included in the window, care-fully chosen to underline the King’s lineage, required particularly careful research, as many of the shields were rare and unknown in London. The compiler of the roll intended to provide small sketches of all of the coats of arms, and while the more familiar English royal arms are all carefully described and drawn, many of the other shields remained blank.

The rise of print and the wider availability of afford-able paper had a significant impact on stained-glass de-sign, introducing patrons to new images and ideas that could be lifted directly from new graphic sources with little mediation through other designers. At the colle-giate church of Holy Trinity, Tatteshall in the last quarter of the 15th century and in the west wall of St. Mary’s,

28 Scholz, Entwurf und Ausführung, p. 181, figs. 258– 62; Butts,

Hendrix, et al. (eds.), Painting on Light, p. 172.

29 Now London, British Library, Yates Thompson, MS 26; Marner,

St Cuthbert, pp. 36– 37. The window was eventually given by

Thomas Langley, Bishop of Durham (1406– 37).

30 London, British Library, Ms. Egerton 4631, rolls A and B;

Rogers, “A pattern for princes”, pp. 318– 38.

31 Marks, Holy Trinity, Tattershall, pp. 191– 200; Brown and

McDonald, Fairford Church, pp. 64– 66.

32 Riviale, “Le vitrail et le jeu des Triomphes”.

33 For other Dürer- inspired Apocalypse windows in the region,

see Vitraux de Champagne- Ardenne, pp. 24, 70– 72, 80– 85,

111– 13, 247– 57, 262– 70.

34 Jones, Balliol College, pp. 48– 49; Wayment, “Wolsey and

stained glass”, pp. 126– 27.

35 Husband, Silver Stained Roundels, pp. 17– 21.




execution of the design in glass, a process undoubtedly facilitated by the greater availability and affordability of paper. In the Kunstbuch, composed in the second half of the 15th century in the Dominican nunnery of St. Kath-erine in Nuremberg, it is recommended that a prelim-inary sketch “auf papir” be sought from a painter.39 In 16th- century Paris, Jean Chastellain was instructed to ex-ecute stained glass after “portraicts et patrons” made by master painter Noel Bellemare.40 The rise of the “celeb-rity” artist undoubtedly encouraged this process, while the increasing affordability of paper, mentioned in the Kunstbuch, meant that even full- size cartoons could be commissioned from artists rather than specialized gla-ziers. The Tuscan artist Cennino Cennini implies that by the late 14th century it was already common practice for Italian glaziers to commission full- scale paper cartoons from well- known artists.41 Paper cartoons could also be stored more easily, meaning that a monumental design could be far more easily preserved across generations. In 1503, York glazier Robert Preston bequeathed “all my scrowles” to Thomas English, while in 1508 glazier and lord mayor of the city John Petty left his “scroes” to his younger brother Robert.42 Outside Italy most of the ev-idence points to the creation of the full- scale cartoons within the orbit of the glazing workshop, and it is to this process that we turn next.

4 Making the Window

4.1 The Glazier’s Table

As discussed above, none of the preparatory drawings of monumental windows to have survived would have been suitable for immediate translation into a window. It is clear that this process was entrusted to the glazier. This is made explicit in the contract of 1447 for the glaz-ing of the chantry chapel of Richard Beauchamp at St. Mary’s church in Warwick. Patterns on paper detailing “the matters, images and stories” required in the win-dows were to be delivered by Beauchamp’s executors to the King’s Glazier, John Prudde in his workshop within the royal palace of Westminster. Prudde was required to see to it that they were “newly traced and pictured by another painter”. The Beauchamp Chapel vidimuses do not survive, but a comparison of those prepared for King’s College chapel and the windows as made, reveal that the glaziers did not slavishly copy them, but made

contracts for the windows at Kings’ College, Cambridge, where the glaziers are directed to the earlier royal glaz-ing scheme in Westminster Abbey’s Lady Chapel.36 Such experience is nowhere better illustrated than in the ex-traordinary correspondence of Birgittine nun Katerina Lemmel, widowed member of the wealthy and influen-tial Imhoff clan of Nuremberg, who entered the cloister of Maria Mai at Maihingen in 1516.37 Through her spirit-ed correspondence with her cousin Hans Imhoff V, she exhorted her family to assist financially in the provision of windows for the newly extended cloister of her nun-nery. In order to engage their enthusiasm and allay their anxieties about cost, she invoked a shared experience of other glazing schemes in the city and vicinity of Nurem-berg, and assures them that the windows will be, above all, spiritually compelling rather than showy and costly. Hers is the only contemporary account of a meeting be-tween a patron and a glazier, in this case Veit Hirsvogel, glazier of the city of Nuremberg, for a meeting that took place in her monastery in May 1518. While the glazier may have brought samples of the subjects favoured by Sister Katerina to the meeting, it is also possible that she had already researched the subjects she wanted, prob-ably in the engravings and devotional woodcuts in the nunnery’s library. She was also very demanding con-cerning the use of abraded ruby glass and metal, rather than wooden window frames, to ensure the longevity of her windows. Sadly, none of them have survived.

Some surviving drawings actually reveal the dialogue between patron and glaziers. Sketch designs believed to have been prepared for Cardinal Thomas Wolsey – a drawing of a 13- light window depicting the Crucifixion and Resurrection now in Edinburgh (Figure 1.3), and 24 drawings outlining a narrative cycle from the Annun-ciation to the Coronation of the Virgin, accompanied by standing saints (now in Brussels) – all bear annota-tions that suggest a discussion concerning alternative arrangements of subject matter.38 The annotations have been attributed to the hand of glazier James Nich-olson, the glazier employed on all of Wolsey’s build-ing projects, and the drawings have been assigned to the chapel of York Place in London and the chapel of Hampton Court respectively. For the Hampton Court east window, Wolsey was even offered two versions of the Crucifixion.

By the end of the Middle Ages there is strong ev-idence of an increasing separation of the role of the designer from that of the craftsman entrusted with the

36 Wayment, King’s College Chapel, pp. 123– 24.

37 Schleif and Schier, Katerina’s Windows, pp. 277– 84.

38 Wayment, “Twenty- four vidimuses”; id., “Wolsey and stained

glass”, pp. 117– 18.

39 Lautier and Sandron, Antoine de Pise, p. 332.

40 Leproux, Vitraux parisiens de la Renaissance, p. 124.

41 See discussion in Thompson, Ch. 21 in this volume.

42 Brown and O’Connor, Glass Painters, p. 55; Knowles, “Medieval

methods of employing cartoons”.



14 Brown

Only two medieval glazing tables have been found and both display some of the characteristics described by Theophilus. One, made of walnut and now cut into two lengths (Figure 1.4), was used to make panels of c.1340 that survive in the choir clerestory of Girona Cathedral (Catalonia), and are preserved in the Mu-seu d’Art de Girona; here, it is the fact that the tables and the windows both survive that makes this a unique phenomenon. The other example, preserved in Bran-denburg Cathedral, is of late 14th century date and originated in Bohemia. It is by comparison very poorly preserved, having been used to reinforce the predella of a medieval altarpiece. Both had escaped international notice until 1986.48 In 2013 the Girona table was reex-amined, using UV light, digital infrared reflexography, and X- ray imaging.49 The whitened upper surface de-scribed by Theophilus as being made of chalk and water was found at Girona to have been made of a surprising-ly resilient mixture of chalk and a proteinaceous binder (perhaps egg or casein). The darkened area immediate-ly below the canopy drawn out on table A was known from earlier UV examination to have originally borne the cartoon of a figure of the Virgin Annunciate.50 The most clearly visible outline is of a geometric design used in several panels in the choir clerestory. Contrary to some assumptions, the table was found not to have been resurfaced between designs but has only a single layer of its chalky coating, meaning that the earlier fig-ure of the Virgin had simply been washed off, allowing another design to be marked in its place, the process alluded to in the Westminster accounts.51 The map-ping of the patterns of square holes, which were left by the glazing nails used to hold glass in place during the leading- up of the painted and fired glass pieces, con-firm that the tables had been used for making several different panels; while some nail holes closely followed the lines of the most visible drawings, others followed earlier patterns that had been washed away. The orien-tation of the drawings and the nail holes, especially on table B, suggest that more than one person had worked on the table at the same time, an observation with in-teresting implications for working practices in the me-dieval workshop.

The reexamination of the table also challenges ear-lier assumptions derived from Theophilus’s descrip-tion, which implies that all details required to make the stained- glass panel were supplied on the table. The

adjustments to the original designs as they translated them into a monumental cartoon.43

For much of the Middle Ages the main vehicle for the full- size working drawing was the glazier’s whitened ta-ble, as described in some detail by Theophilus. The ta-ble was a multi- functional component in the process of design and manufacture, for it served successively as a cartoon, a cut- line drawing and a work- bench on which to lead- up and solder the finished window. In a 1443 in-ventory of the materials stored at the royal residences at Westminster and Sheen, for example, two “portreying tables of oak, two tables of poplar and 11 trestles used for glazing works” are listed.44 They were valuable com-modities, and in 1458 York glazier Robert Shirley’s father bequeathed to him his “tables and trestles [that] belong in any way to my craft”.45 Even in the 18th century, Pierre le Vieil, a member of a glazing dynasty, placed the gla-zier’s table at the top of his list of essential equipment for a glazier’s workshop.46

The glazing accounts for St. Stephen’s Chapel, West-minster, make explicit the value placed on the prepara-tion of the glazier’s table and the status accorded to those who fulfilled the role. Master glazier John de Chestre con-sistently received the highest wages of all the glaziers. He worked with five others, also termed master, all of them defined by their role in “designing and painting on white tables”, which were washed with ale at regular intervals throughout the project, allowing new designs to be drawn up on their whitened surfaces. 47 In the hierarchy of pay-ments made to the glazing team employed at Westminster, the designing on the white tables was always entrusted to those termed “master” and was most generously reward-ed, at 12d per day. Glass- painters were paid only 7d per day, while those engaged in “breaking and fitting glass” were paid 6d. Just over 50 years later, in 1405, master glazier John Thornton of Coventry was obliged entirely “with his own hands to portrature [portreiabit] the said window”, although he was allowed to delegate glass- painting tasks to others. It is not hard to see why this process was so high-ly prized, as it was the glazier’s table that determined the relationship of the window as made to the sketch designs authorized by the patron. It also controlled all the other technical processes leading to the creation of a satisfac-tory monumental window, a sequence of processes that would involve several workshop members.

43 Boon, “Two designs for windows by Dierick Vellert”, pp. 153–

56, 204– 05; Wayment, King’s College Chapel, plates 129,

135, 137.

44 Salzman, “Medieval glazing accounts”, p. 27.

45 Knowles, “The Chamber family”, pp. 127– 28.

46 Le Vieil, L’Art de la peinture sur verre, p. 137.

47 Salzman, “St Stephen’s Chapel”.

48 Vila Grau, “La table de peintre- verrier”, pp. 32– 34; Maercker,

“Überlegungen zu drei Scheibenrissen”.

49 Santolaria Tura, Glazing on White- Washed Tables.

50 Ainaud de Lasarte et al., Catedral de Girona, pp. 74– 79.

51 Caviness, Stained Glass Windows, p. 50.




widely across a single panel, usually all orientated in the same direction. Once the bespoke nature of the cut-ting of the glass for each panel is appreciated, it can be seen that after firing the glaziers needed to reassemble the pieces belonging to each specific “jigsaw puzzle” of painted and fired glass with speed and precision. While large, distinctive pieces belonging to unique figures or narrative compositions could probably be recognized easily, repeated elements within a scheme could be less quickly distinguished from one another, and although there were superficial similarities, glass pieces were not readily interchangeable from one panel to another, even if prepared on the same glazier’s table.54

4.2 Cutting the Glass

Both Theophilus and Antonio da Pisa provide descrip-tions of glass- cutting techniques, and yet only recently have these been subjected to critical examination. Both writers assume that the cutting of glass is done directly on the glazier’s table without the intermediary of a tem-plate. Light- coloured glass could be laid directly over the dark lines drawn on the table, but for cutting dark glass, marks were first outlined on a piece of white glass, which could then be held up together with the dark in order to allow the necessary outlines to be seen against the light.

Theophilus outlines two processes, the cutting of glass with a heavy, hot iron (“thin throughout but thicker at one end”) and the shaping of glass with a flat, notched grozing iron (“a hand’s- breadth in length and curved back at each end”),55 a tool that crops up in the St. Ste-phen’s chapel accounts on numerous occasions, and was apparently supplied to the glaziers from a common store of tools.56 The hot iron (known in German as the “divid-ing iron”) was very similar to the tool used for solder-ing: were these tools used interchangeably? The dividing iron or soldering iron is represented arranged in saltire (with the more distinctive grozing iron) in the borders of the 16th- century ordinances of the Guild of St. Luke in Antwerp.57 Before the advent of the diamond cutter, only the dividing iron could be used to cut glass into two or more pieces without any great loss of material, for the grozing iron shapes glass by reducing it in size. It was long assumed that its apparently cumbersome size and shape meant the dividing iron could be used for cutting glass only to very approximate shapes, but experimen-tation conducted during the Antonio da Pisa project

evidence of the Girona table shows that a significant degree of autonomy was afforded the individual glazier, even after the skeleton of the window design has been determined by the master. While the table is marked with letters that might refer to the colours of glass to be used, these do not readily correlate with the wide array of glass colours found across the six canopies that de-rived from the design on table A, while the only painted element to have been drawn in detail is the vine leaf mo-tif that decorates the gable of only two of the six cano-pies. This suggests either that detailed instructions on glass colour and exact positioning of the painted line were available to the glazing team in another form, or more likely, that in a close- knit experienced team, a level of decision- making was delegated to individual crafts-men and painters.

The designs on the table do not actually indicate all the lead lines at all, and, indeed, leave out some lines that would be critical to the cutting of glass for a viable stained- glass panel. The master therefore allowed the in-dividual glazier to judge where to place subsidiary lead lines and thus how best to cut a piece of glass, ensuring that sheets could be cut economically and without waste. This realization has important implications for our un-derstanding of working relationships within the team, but also for the status of individual components within the whole glazing scheme. While based on a single de-sign “template”, the Girona canopies are anything but a mass- produced product. Each one is, in effect, unique, a version of the master’s cartoon rather than a replica of it, and this is borne out by close comparison of the glazier’s table with the surviving stained glass presumed to have been made on it. The superimposition of the actual cut-line of the glass of several of the canopies onto the lead lines indicated on table A shows that glass was cut and leaded in a variety of different combinations. Hérold ar-rived at similar conclusions based on close examination of panels of the same design, apparently indebted to the same cartoons, in a number of churches in the Cham-pagne region.52

This adaptive approach to manufacture goes a long way to explain the ambiguous “glaziers marks”: discreet and barely visible marks usually painted on or wiped off a fired paint layer, and predominantly found in the more “anonymous” areas of a panel, including architectural frames and backgrounds.53 While some glaziers’ marks may have indicated the order of assembly, this cannot explain the large numbers of the same mark scattered

52 Hérold, “ ‘Cartons’ et pratiques d’atelier”.

53 Armitage Robinson et al., “Marks on the glass at Wells”;

Wayment, “The glaziers’ sorting marks at Fairford”; Vila

Delclòs, “Les marques d’assemblages”.

54 Cothren, “Production practices”.

55 Theophilus, The Various Arts, pp. 48– 49.

56 Salzman, “St Stephen’s Chapel”, (1926), p. 32; (1927),

pp. 38, 40.

57 Caen, Production of Stained Glass, pp. 301– 03.



16 Brown

prophets painted after 1132 for the clerestory of Augsburg Cathedral (see Figure 2.5), reveal a glass- painting craft al-ready fully mature and perfectly mastered.61 By 1140, Ab-bot Suger of Saint- Denis was able to call on glass painters from several countries to work at his abbey church.62 The materials used in 12th- century Germany for painting the glass are described by Theophilus as a finely ground mix-ture of burnt copper filings and a flux of green and blue glasses. In late 14th- century Italy, Antonio da Pisa also rec-ommends copper- filings but advocates the use of yellow glass rosary beads for the glass flux. In both the 12th- century text and the late 14th- century one, the proportion of the paint mix is specified as one- third copper to two- thirds glass, and produced a brown or black paint.63

Glass paint can be diluted but not dissolved, and the choice of binder determines the consistency, flow, and workability of the painting medium. The paint remains slightly granular, even after thorough grinding. Theoph-ilus advises the use of wine or urine as a binder for the powdered glass- paint, while Antonio recommends a tempera binder mixed with sap from the fig.64 The St. Stephen’s Chapel accounts refer to glass paint as “geet” and “arnement”, and also include payments for the gum arabic that helps the paint to adhere to the glass before it can be fired.65 The organic binders necessary to carry the fusible pigment are burnt away in the firing process (stained glass is usually fired at 600– 50°C), and so do not survive to be subjected to modern analysis. None-theless, the development of glass- painting techniques in the later Middle Ages, resulting in a complex and multi- layered approach to the application of paint, means that more than one binder must have been used to avoid one layer running into and dissolving another. One layer can be applied with a watery binder – wine, water, or vine-gar – and another with an oily binder, such as lavender or clove oil. Close examination of multi- layered paint applications confirm that medieval glass- paint was fired only once, as highlights can be seen to have been cut through all the layers of paint to the underlying base glass, impossible to achieve once a paint layer has been fired (Figure 1.8).

Throughout the Middle Ages the predominant paint-ing technique was to begin by laying down a thin overall

revealed the sophistication of this tool when wielded correctly, allowing glass to be cut at angles impossible to achieve with the diamond.58 The large size of the iron’s head is required in order for it to be heated to a red- hot temperature (750°C) and then to retain this heat for the duration of the cutting process. The glass is not cut so much as divided, by a crack generated by thermal stress (Figure 1.5), and the skill lies in encouraging the crack to flow across the sheet in pursuit of the head of the hot iron. The resulting cut edge is far softer and more con-genial to work with than the sharp edge cut by the dia-mond or modern cutting wheel.

The same can also be said of the edge produced by the grozing iron, which nibbles back the glass in a se-ries of small shales that results in a scalloped and slight-ly chamfered edge that is far less sharp that a modern cut (Figure 1.6). The grozing iron can be used with great speed and precision, and one of the hall- marks of a me-dieval stained- glass panel is the closeness of the fit of its complex and tightly interlocking pieces. The visually distinctive grozing iron was widely used as a heraldic de-vice in the armorials adopted by glaziers and their guilds (Figure 1.7), and yet despite the numerous contemporary images of them, they had little intrinsic value and very few have survived.59

Antonio additionally describes the use of a range of hard stones, including the diamond, which had been widely adopted as the main tool for cutting glass by the early 17th century.60 The diamond glass- cutter was a more costly tool than the grozing iron and, as it responds to the pressure of the hand of the individual, it became a far more prized and personal tool than the grozing iron, and consequently less likely to appear in a general workshop inventory. It may therefore have been in use at an earlier date than the surviving inventories suggest. However, it is also clear from the illustrations published by Diderot (1751– 77) and Le Vieil (1774) that the groz-ing iron continued in use alongside the diamond glass- cutter well into the 18th century.

4.3 Painting the Glass

As we have seen, the painting of the glass, that process that distinguishes stained glass from a purely mosaic process, was not ranked as highly within the workshop hierarchy as the process of design. It remains, however, the aspect that most enchants and engages the viewer. The extraordinary monumental windows with figures of

58 Lautier and Sandron, Antoine de Pise, pp. 97– 104.

59 One is preserved in the Germanisches Nationalmuseum in

Nuremberg. Azzola, “Das historische Handwerkszeichen eines

Glasers”.


61 Becksmann, “Die Augsburger Propheten”, pp. 84– 110. Also

see Dell’Acqua, Ch. 2 in this volume. For even earlier archaeo-

logical evidence see Balcon- Berry et al. (eds.), Vitrail, verre et

archéologie.

62 Abbot Suger, On the Abbey Church, p. 73.

63 Theophilus, The Various Arts, p. 49; Lautier and Sandron,

Antoine de Pise, pp. 107– 09, 307– 38.

64 Theophilus, The Various Arts, p. 49; Lautier and Sandron,

Antoine de Pise, p. 112.

65 Salzman, “St Stephen’s Chapel”, (1926), p. 14.




was adopted in the course of the 14th century, becom-ing ubiquitous and even dominant in the 15th century, the late adoption of silver stain by stained- glass artists is rather surprising. It is mixed with an ochre binder, and so was usually applied to the exterior of the glass to avoid damaging the painted details on the interior sur-face. By the end of the Middle Ages coloured vitreous enamels – transparent pigments created from a finely ground, low- melting coloured glass – provided a new range of colours that could be applied with the brush.70 These were popularly used to colour the increasingly in-tricate charges of heraldic shields and to enliven small- scale panels and roundels designed to be seen at close quarters, freeing the glazier of the need to cut and lead- in small pieces of glass of different colours.

Guild prohibitions suggest that glass painters also used cold, unfired paint to augment their fired decora-tion, perhaps when they had omitted a fired detail, or had underfired their conventional paint or stain. Anto-nio provides a recipe for cold paint made of verdigris mixed with a liquid varnish, which when allowed to dry in the sun took on the appearance of a fired paint.71 A 15th- century English manuscript mentions an oil- based recipe for a paint suitable “To make curyus worke on glasse wyndowes after the be aneled”.72 The inherent-ly poorer durability of unfired cold paint and the failure of careless restorers to recognise its antiquity, means that its use has been overlooked. However, prohibitions against its use demonstrate that it must have been rec-ognised as a common enough technique, attested by sig-nificant survival in windows in Nuremberg and Berne.73

4.4 Further Embellishments: Applied

and Inserted Jewels, Abrasion

A small but technically demanding range of further em-bellishing techniques were available to the medieval glazier. Theophilus mentions one of these, the use of a thick application of glass- paint to the surface of a piece of glass of one colour as a means of fixing through firing a small piece of another colour to its surface.74 This “ap-pliqué” approach was used over a very long period, and is most frequently used to imitate the application of jew-els to the hems of vestments and rich garments or to the brim of a crown or mitre (Figure 1.10). Examples dating

glaze or wash of paint, to which subsequent layers were applied in order to modify the passage of light through the glass. Glass paint dries quickly and so needs to be applied with spontaneity and confidence. It can be mat-ted, stippled, and textured with a variety of brushes and tools. The layered painting technique means that error cannot easily be corrected, as glass painting is both an additive and a reductive process. Glass paint applied with a brush can also be etched and scratched out to cre-ate piercing highlights. Nuremberg glass- painters of the 16th century could buy brushes made of silver wire for this purpose, although more mundane objects such as quills, needles, and the sharpened ends of brush handles were also used.66 The semi- opaque contour lines (trace lines) are applied last of all, in a process that seems to be counterintuitive and is extremely difficult to achieve. Its great advantage lay in the fact that this technique re-quired only a single firing.

Only in recent years, and through the close observa-tions made by conservators and art historians, have the ways in which the medieval glass painters worked be-come clearer. On the exterior surfaces of painted glass dating from the late 13th to the early 16th century, faint and sometimes partially expunged lines, coinciding with the outlines painted on the interior surfaces of the glass, have been observed.67 These represent temporary guidelines, traced off the glazier’s table or cartoon, al-lowing the glass painter to remove the individual glass piece from the table so that the painting could be car-ried out against the light, working with an exterior out-line of a design that would only take its final form on the interior surface of the glass with the final application of the trace line. The glass painter would normally erase these temporary guidelines before firing the glass, but in some cases failed to remove them adequately so that, having also been created using fusible glass paint, they were inadvertently fired onto the finished piece.68 Glass painters also deliberately took advantage of the fact that glass can be painted on both of its surfaces, allowing a play of optical effects to be achieved.

From the years around 1300 it was also possible to add a yellow colouring to glass through the application to the exterior surface of a window of a silver nitrate or ox-ide compound derived from ground silver filings ( Figure 1.9).69 Given the alacrity and enthusiasm with which it

66 Butts, Hendrix et al. (eds.), Painting on Light, pp. 57– 65.

67 Trümpler, “Rückseitige Vorzeichnungen auf Glasgemälden”;

Ayers, Merton College, pp. lxxv, 25.

68 Cothren, “Production practices”, pp. 122– 27.

69 Salzman, “St Stephen’s Chapel”, (1926), pp. 32, 33, 34; Lautier

and Sandron, Antoine de Pise, pp. 109– 12; Also see Husband,

Ch. 19 in this volume.

70 Caen, Production of Stained Glass, p. 139. The enamel layer

can be as little as 5– 100 microns thick.


72 Brown and O’Connor, Glass Painters, p. 61.

73 Marks, Stained Glass in England, p. 39; Hör, “Kaltmalerei auf

Glasgemälden aus Nürnberg um 1500”; Trümpler and Wolf,

“Cold paint on the late medieval choir windows of Berne

Minster”.

74 Dodwell, Theophilus, pp. 57– 58.



18 Brown

nitric acid will etch glass with a high lime content and that hydrofluoric acid may have been in use far earlier than hitherto supposed.79

4.5 Firing the Glass

Only with the firing of the glass could the delicate paint-ed detail be secured to the surface. This was the stage at which all the hard work of the glazing team could be lost, as the medieval kiln could not be easily controlled and poor firing could result in underfired paint and/ or broken pieces. The treatises, not surprisingly, devote a considerable amount of space to the construction of the small firing kilns and to the firing process.80 While no temperature or firing duration is specified, it is clear that the glaziers understood the performance of differ-ent glass types and glass sizes inside the kiln. The careful preparation of the fuel, the management of the ventila-tion of the kiln interior, and the placement of glass on a kiln pan well- lined with an insulating layer of chalk and ash, would ensure efficient firing of the glass. Antonio advises “never put any red or yellow at the bottom, and don’t put them too near the edges of the pan as both co-lours are very fearful of the fire; nor should you put large pieces at the bottom or near the edges of the pan”.81 Both Theophilus and Antonio suggest that the glazier recognised a successful firing from the colour of the kiln interior and the pan on which the glass was laid out. For reasons of economy, glass was often stacked in layers in the kiln, and traces of paint and silver stain inadver-tently transferred from one layer to another are often observed.82 The use of uneven and kiln- deformed piec-es in some medieval windows, normally in subsidiary openings, underlines the glaziers’ reluctance to dispose of expensive materials, but also suggests that accidents in loading the kiln did happen.83

4.6 Reassembling and Glazing the

Panels: Lead and Solder

After the firing and annealing of the glass, all the pieces were reassembled on top of the original glazier’s table. It is now clear why Theophilus advocated a table large enough to hold two panels of glass, as the pieces could be laid out on one part of the table and then transferred

from the 12th to the 15th centuries have been identified with their jewels still attached.75

A more permanent but even more demanding tech-nique involved the introduction of small glass insertions, held in lead, introduced into holes drilled into the base glass, a highly risky procedure that, not surprisingly, be-came one of the tests of mastery of the glazier’s craft, and is found in glass from the mid- 15th century onwards. The treatises are almost entirely silent on this technique, in part because of its late adoption, but perhaps also be-cause it was one of the “mysteries” of the profession. The 15th- century Nuremburg Rezeptsammlung implies the use of a lead drill of some sort, used with an emery grind-ing powder, and recent unpublished research has shown this to be a viable technique.76 While these insertions are most commonly small and circular (Figure 1.11), once the base glass was breached, a small grozing iron could be introduced to enlarge and shape the hole ready to take a larger insertion of a more complex shape.77

From the late 13th century onwards grinding or abra-sion was also a technique widely employed to modify the upper coloured surface of ruby glass. No technical treatise addresses this technique, but the tiny scratch-es on the surface of ruby glass treated in this way show that a grinding tool was used to scratch away the thin surface layer of flashed red glass in order to create a decorative pattern or heraldic device. The white base glass revealed thereby could also be enlivened with sil-ver stain. Antonio da Pisa describes a far less labourious method, involving a wax resist and the application of “water for separating gold and silver, some of the wa-ter that goldsmiths sell” with which the red coloured surface of a flashed ruby could be removed after 2 or 3 hours.78 Recent research has not only uncovered a sur-prisingly large number of examples of early acid- etched pieces of stained glass (Figure 1.12), but has shown that

75 The 12th- century examples are said to survive in Regensburg

Cathedral (personal communication, Sebastian Strobl).

Early 13th- century examples were identified in the glazing

at Heimersheim an der Ahr in Germany: Kowolik, “Choir

windows of St Mauritius in Heimersheim”. Unpublished

examples can be found in the choir aisles of York Minster of

c.1370 and c.1440 (windows siv and svii), while heraldic

panels of the mid to late 16th century from Fawlsey Hall, in

Northamptonshire, now in the Burrell Collection in Glasgow,

employ a variation of this technique.

76 Lautier and Sandron, Antoine de Pise, p. 338; Stacey, “Artistic

and technical dexterity”.

77 At Fairford, both circular and quatrefoil insertions are found.

See Brown and MacDonald, Fairford Church, plates 30 and 31.

78 Lautier and Sandron, Antoine de Pise, pp. 119– 22. The 15th-

century Bolognese manuscript seems to be referring to the

same material: Merrifield, Original Treatises, pp. 494– 95.

79 Pilosi et al., “Early acid- etching”.

80 Theophilus, The Various Arts, pp. 51– 52; Lautier and Sandron,

Antoine de Pise, pp. 135– 41.



82 Cothren, “Production practices”, p. 123; Ayers, Merton College,

p. lxxv.

83 In the tracery lights of n6 in the Chapel of New College,

Oxford, for example. Observed 2009 by conservators of the

York Glaziers Trust.




and finer than modern leads, often only 4 mm- 6 mm across the flange, meaning that they could easily be bent around the most intricate and tightly- fitting of shaped glass pieces, an essential and symbiotic relationship in the most sophisticated stained- glass designs. Indeed, the glass and lead fitted together so closely that windows were watertight without the need for any waterproof-ing putty, which only became ubiquitous following the adoption of lead milling techniques from the later 16th century onwards. The Cologne lead nets are particularly interesting because their hearts have been packed with “withies”, which act as spacers when leads were doubled to give greater strength or greater visual emphasis to as-pects of the design, but also served to give the panels greater resistance to wind pressure.88

The glazier used “closing nails”, described by Theoph-ilus, with which glass and lead is held in place during the assembly process.89 Each intersection in the leading pat-tern was made firm by the application of solder on both sides of the panel, an alloy of tin and lead, cast into thin rods for ease of application. This low- melting material, for which Antonio provided several recipes, flows across and into the joints between leads, although care was re-quired in moderating the temperature of the soldering iron so as not to melt the lead cames.90 The application of a flux to the joint helped the solder to flow, and in the St. Stephen’s Chapel accounts, tallow (rendered beef or mutton fat) was purchased for this purpose.91

The lead matrix was given extra strength by the gla-zier’s skill in integrating the lead and the glass. Well- designed panels avoid too many vertical and horizontal straight lines, which provide weak “hinge” points in the lead matrix. Glass- painters frequently edged their glass pieces with a dense back trace- line. This registered the permissible limits that could be occupied by the lead flange, perhaps allowing the glaziers some leeway in grozing the painted pieces after firing to ensure a bet-ter fit. In unpainted geometric glazing, of a kind often associated with Cistercian patronage, the design re-lies entirely on the subtle relationship between glass and lead- line, and reveals the extraordinary precision in cutting and leading that the best glaziers could achieve.92

to the “cartoon” as the leading- up proceeded. In the effi-cient sorting of the glass pieces from the kiln pans back into their specific panels, the discreet sorting marks dis-cussed above would have been invaluable. The glazier would then begin the process of leading the pieces to-gether using H- profiled lead strips (usually called cames) to hold adjoining pieces together. Lead is the perfect ma-terial for this job, being malleable and capable of being cast into sections of different thickness, depending on whether a wider outer lead or thinner internal lead was required.

Medieval window lead was cast in moulds, a process described by both Theophilus and Antonio.84 While a variety of materials for mould- making are mentioned, including an iron and copper alloy, wood, and a variety of stones, Antonio suggests that they should be procured from a master in the craft. He personally favoured those made of an alloy of copper and lead, describing them as both more durable and more responsive to thermal ex-pansion. Wooden moulds would not have survived for long, while hard stones were prone to break when sub-jected to repeated heating during the casting process. In excavations at Saint- Denis and Reims in France, moulds made of chalk for casting window leads have been found, with associated lead strips.85 The leads found in associ-ation with these moulds retain the vestiges of the cast-ing flashes that would be planed off before use. Stone or chalk moulds could have been prepared by the glaziers themselves, while a metal mould would have to be forged by a blacksmith. Surviving medieval window lead, now relatively rare as a consequence of subsequent resto-rations (Figure 1.13), often displays a faceted edge to the “leaf” (or flange) of the lead, where it has been scraped clean of any casting flashes left from the mould. Pin- prick holes in the lead’s heart are evidence that air had been trapped during casting; Antonio proposed reducing this risk by greasing the mould interior prior to use.

After centuries of neglect and destruction, medieval window leads are now increasingly studied and prized.86 Compared to modern milled and extruded lead, their strength and resilience is remarkable. Those in the win-dows of the choir clerestory of Cologne Cathedral are now over 600 years old.87 They were usually far thinner



85 Deneux, “Un moule à plomb”, pp. 149– 54; Meyer and Wyss,

“Des moules à plomb”, pp.105– 06. For stone moulds, see

Baker, Excavations at Selborne Priory, pp.105– 08.

86 Knight, “Researches on medieval window lead”; Cuzange and

Texier, “Caractérisation des plombs anciens de vitraux”.

87 Brinkmann, “Die Verbleiung und Befestigung der mittlealterli-

chen Farbverglasung”.

88 Similar spacers have also been noted at Altenberg and

Haina: Cortes Pizano, “Medieval window leads”, p. 27, n. 10.

89 Theophilus, The Various Arts, pp. 56– 57. The Girona table

bears the nail holes from the process of panel assembly.


91 Purchased from the appropriately named Peter Bocher:

Salzman, “St Stephen’s Chapel” (1926), p. 35.

92 Zakin, French Cistercian Grisaille Glass; Brown, York Minster,

pp. 18– 19.



20 Brown

5 “Walls Like Unto Clear Glass”

Stained glass is now one of the most important surviv-ing manifestations of medieval monumental painting. Its status in the Middle Ages relied in no small measure on its capacity to turn the medieval church building into a foretaste of the heavenly Jerusalem described in John’s vision (Revelation 21:18). While those who practised this craft remain elusive, collaborations between art histori-ans, textual and documentary scholars, materials scien-tists, craftsmen, and conservators have transformed our understanding of medieval stained glass making, shed-ding new light on the role of the master, the autonomy of the craftsman and the relationship between patron-age, design and execution.

Bibliography

Primary Sources

Abbot Suger, De administratione, de consecratione, ordinatio,

ed. and trans. E. Panofsky, On the Abbey Church of Saint- De-

nis and its Art Treasures, 2nd edn. by G. Panofsky- Soergel,

Princeton, New Jersey, 1979.

Anonymous Author, Kunstbuch de Nuremberg, transcrip-

tion after E.E. Ploss, “Ein Buch von alten Farben”, trans.

B. Kurmann- Schwarz and C. Lautier, in C. Lautier and D.

Sandron (eds.), Antoine de Pise. L’art du vitrail vers 1400 (CV

France, Études, 8), Paris, 2008, pp. 331– 35.

Anonymous Author, Rezeptsammlung of Nuremberg, ed.

S. Matter, transl. B. Kurmann- Schwarz and C. Lautier, in

C. Lautier and D. Sandron (eds.), Antoine de Pise, pp. 337– 38.

Antonio da Pisa, Secreti per lavorar li vetri, eds. D. Gallo and

D. Sandron, trans. K. Bienvenu and C. Lautier, in C. Lautier

and D. Sandron (eds.), Antoine de Pise, pp. 41– 78.

Le Vieil, P., L’Art de la peinture sur verre et de la vitrerie, Paris,

1774.

Merrifield, M.P., Original Treatises on the Arts of Painting,

2 vols., New York, 1967.

Myers, A.R. (ed.), The Contracts for the Making of the Tomb

of Richard Beauchamp, Earl of Warwick 1447– 54 (English

Historical Documents 4 (1327– 1485)) London, 1969, part 4,

document 686.

Theophilus, Theophili, qui est Rugerus, prespyteri et monachi,

libri III, De diversis artibus seu Diversarum artibus schedu-

la, ed. and trans. R. Hendrie, An Essay Upon Various Arts

in Three Books by Theophilus called also Rugerus, Priest and

Monk, London, 1847.

Theophilus, De Diversis Artibus, ed. and trans. C.R. Dodwell,

Theophilus, The Various Arts, London, 1961.

Theophilus, De Diversis Artibus, trans. J.G. Hawthorne and C.S.

Smith, On Divers Arts: the Foremost Medieval Treatise on

Painting, Glassmaking and Metalwork, New York, 1963.

4.7 Fixing the Windows: Stone and

Iron, Masons and Blacksmiths

In fixing a medieval window the glaziers, by necessity, worked closely with masons and blacksmiths. While this collaboration is largely passed over in the treatises, it is far more apparent in the glazing accounts. In the 12th and 13th centuries, before the advent of subdivided stone tracery, stained-glass panels were held in position in the window opening in a wrought- iron armature set into a wooded frame rebated into the stone.93 Panels were held in place by projecting lugs through which wedges or curved pins were threaded. The Canterbury armatures are extraordinarily complex in their shape, and would have required close liaison between glaziers and blacksmiths to ensure a close fit.94

Once window openings were subdivided by stone tracery, new fixing systems developed. Masons provided glazing grooves around the jambs and heads of their win-dow mullions into which the stained- glass panels, made slightly wider than the visible opening, could be slotted directly, then mortared in place for a watertight finish. Horizontal iron support bars – lug bars or T- bars – were introduced at intervals in order to support the weight of the glazed panels. Additional vertical and horizontal bars were not load- bearing but provided additional strength-ening. Lead ties, soldered at appropriate intervals across the stained- glass panels, allowed them to be tied to these bars, increasing their resistance to wind pressure. While the ferramenta could be set into sockets cut into the ma-sonry, the window bars sometimes run through all the mullions of the window opening and so must have been introduced during the initial construction of the window, with implications for early project planning and the in-teractions between glaziers and masons. The relationship of the stained- glass panel to its fixing system could never be treated as an afterthought, but required careful plan-ning to ensure that the ferramenta did not interfere with major design features. Some surviving medieval designs indicate the location of the ferramenta, and Antonio of-fers advice about the placing of the bars and ties.95 There is even reason to believe that in some cases the mason-ry was designed to reflect the iconography of the stained glass it was to support, although this must have been at the stipulation of the patron.96

93 This sort of fixing system continues in use in Canterbury,

Lincoln, and Salisbury cathedrals.

94 Marks, Stained Glass in England, p. 38, fig. 29.

95 Lautier and Sandron, Antoine de Pise, pp. 49, 71.

96 The masonry of York Minster’s Great East Window, for exam-

ple, appears to have been adjusted deliberately to reflect the

numerological significance of the window’s stained- glass

imagery: Norton, “Sacred space and sacred history”.




Cortes Pizano, F., “Medieval window leads from Padralbes

(Catalonia) and Altenberg (Germany): a comparative

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